The intent is to investigate factors such as size of the fungal cell and presence of fungal polysaccharide that may influence infectivity and virulence of species of Filobasidiella (equals Cryptococcus neoformans), and to determine the nature of innate resistance in normal healthy individuals to this organism. The main thrust will be to examine some host responses to intact fungus and to components thereof, both particulate and soluble; in particular, histologic events in situ in the pulmonary bed and other body sites. Experimental systems will include phagocytosis in vivo and in vitro, and chemotaxis. Results will be evaluated in relation to other closely related capsulated yeasts and components thereof. One of the important modes of animal inoculation will be by exposure to aerosols.